RCBO tripping

[eagleeye]

Hi guys i am trying to test my new installation for the Zs valves but the RCBO's just trip out on test. The meter i have is a di-log 9083P multi tester which has the non trip function for this reason. I used it to test another circuit on a different job and that was fine and did not trip. That was a "Square D" RCBO. My ones are "Wylex" RCBO's. Has anybody else encountered this problem and if so how can i test for Zs values without it tripping ?

 

[DurhamSparky]

Hi guys i am trying to test my new installation for the Zs valves but the RCBO's just trip out on test. The meter i have is a di-log 9083P multi tester which has the non trip function for this reason. I used it to test another circuit on a different job and that was fine and did not trip. That was a "Square D" RCBO. My ones are "Wylex" RCBO's. Has anybody else encountered this problem and if so how can i test for Zs values without it tripping ?

i got dilog as well!!! nice little meter!

R1+R2 + ZE = ZS!!!!

 

[pevvers]

Well if you cannot test it without tripping, you would have to either swap it for an MCB to do the test, do the old favourite R1+R2+Ze=Zs, which I'm sure enough people will tell you that that's not correct, or but a better test instrument (my Megger has yet to trip an RCD).

It could be that the RCD is faulty though, and have you disconnected all the loads before testing?

 

[DurhamSparky]

whats wrong with R1/R2 +Ze???

i though it was Zs - Ze = R1R2 that was not allowed!!???

 

[pevvers]

I personally don't see anything wrong with that, and have actually been told by my NICEIC area engineer that for radials to spurs etc. to test is this way is safer and the better way to do it. He also said that for PIR's then R1+R2=Zs-Ze is also acceptable.

I just know that there are people in two distinct camps when it comes to calculation!

 

[DurhamSparky]

i got wrong off my elecsa assessor for working out zs-ze=R1R2

he noted that on his paperwork for next year!

 

[pevvers]

I find it strange how different schemes and even different engineers in the same scheme can have such differing views. Especially as these are meant to be the guys with all the knowledge, so you would think that they'd think more or less the same way.